Selectize is the hybrid of a textbox and <select> box. It's jQuery based and it has autocomplete and native-feeling keyboard navigation; useful for tagging, contact lists, etc.
A cross browser rich text editor with an API
Multiple file upload plugin with progress-bar, drag-and-drop.
jQuery Validation Plugin
lightweight jquery date selector with multi-language support
It's a new file uploader solution!
jQuery Form Plugin
Add Github like mentions autocomplete to your application.
In-place editing with Twitter Bootstrap, jQuery UI or pure jQuery
Email domain spelling suggester
A jQuery Plugin to make masks on form fields and HTML elements.
The missing components for your favorite front-end framework.
A JS library for building WYSIWYG editors for HTML content.